Polymeric acetals and process of making same



aienied Oct. 30, 1945 M150 STATES PATENT OFFICE POLYMERIC ACETALS AND PROCESS OF MAKING SAME .ioseph Dahle, West Newton, Mass, assignor, by mesne assignments, to Pro-phy-lac-tic Brush Company, Northampton, Mass., a corporation of Delaware No Drawing. Application October 30, 1942, Serial No. 463,943

6 Claims.

ization is produced by the action of an aldehyde dissolved in an organic liquid which is a non-solvent for the polyvinyl alcohol and the reaction proclugt but probably at least a partial solvent for the reactive agent, e. g. an aldehyde. A liquid hydrocarbon is suitable for the purpose. I may prefer to pretreat the base material with a catalyst, such as sulfuric acid, dissolved in a liquid, such as methanol, which is a non-solvent for the base material and non-reactive therewith. This is particularly desirable when the catalyst tends to produce a discoloration of the aldehyde when added directly to the aldehyde solution. Otherwise, the catalyst may be added to thealdehyde solution. Sometimes, the addition of an auxiliary liquid, such as acetic acid, may beused to increase the reaction rate or the degree of reaction or both.

The invention will be further illustrated by the following specific examples.

Example No. 1

Residual alcohol groups Parts by No. Composition of reaction mixture weight Example N0. 2

A lo-gram sample of comminuted polyvinyl alcohol sheeting same as used in the preceding example was refiuxed on a water bath for 4 hours in a reaction mixture consisting of toluol 100 grams, butyraldehyde 20 grams and ammonium sulfate 3.6 grams. After purification the residual alcohol groups calculated as vinyl alcohol were determined and found to be 28.2%. This result indicates that when butyraldehyde which is soluble in toluol is used as the reactive agent the reaction proceeds satisfactorily even without auxiliary liquids such as acetic acid.

Example No. 3

Two samples of polyvinyl alcohol sheeting 0.001 in. thick containing 17% dry basis of glycerine as plasticizer were wound on stainless steel screens, dried for one hour in an oven at 100 C.

and then reacted in baths of the same composi tion, one for 2 hours at 73 C. and the other for 17 hours at room temperature. The composition of the baths was in each case:

Grams Toluol 600 Acetaic acid glacial 300 Paraformaldehyde 30 Ammonium sulfate 18 Example No. 4

Powdered polyvinyl alcohol was screened through an mesh sieve, oven dried overnight at 70 C. and 88 grams weighed out and added to a solution of 6.5 grams sulfuric acid in grams methanol and mixed thoroughly, followed by air drying at '50" C. until the final weight was 102 grams. This quantity was charged to a mixture of 66 grams of paraldehyde in 500 grams mineral spirits and the temperature brought to 7 0 C. and maintained there for four hours. After standing overnight at room temperature the reaction product was washed, neutralized, purified, stabilized and dried. By analysis it showed 12.1% unreacted alcohol groups calculated as vinyl alcohol. It was a white powder completely insoluble in water, hot or cold.

Example N0. 5

Powdered polyvinyl alcohol was screened, dried and treated with sulfuric acid and methanol as,

in Example No. 4 and 60 grams of this treated polyvinyl alcohol reacted with 65 grams crotonaldehyde in 300 grams mineral spirits at 70 C. for three hours. After purification, drying and analysis this reaction product was found to have 18.0% unreacted hydroxyl groups calculated as vinyl alcohol. The reaction product, a white powder, was totally insoluble in water, hot or cold.

Example No. 6

Powdered polyvinyl alcohol, acidified and dried was screened, as in Example No. 5, and 100 grams reacted with 150 grams furfuraldehyde in 500 grams mineral spirits at 70 C. for three hours. The reaction product, a dark brown powder, was insoluble in hot or cold water and showed by analysis 22.9% unreacted hydroxyl groups calculated as vinyl alcohol.

Example No. 7

Powdered polyvinyl alcohol was pretreated, as in Example No. 5, and 90 grams, thus treated, were reacted with 89 grams butyraldehyde in 500 grams mineral spirits. The reaction was started at 26 C. (room temperature). Without external heating the temperature rose to 40 C. and remained there for three hours. A sample purified and dried showed 7.7% unreacted alcohol groups calculated as vinyl alcohol. It was a white powder insoluble in water, hot or cold.

Example No. 8-

Example No. 9

Four samples of polyvinyl alcohol sheeting 0.003 inch thick were soaked for 30 minutes in a 5% solution of sulfuric acid in methanol and dried overnight at room temperature. Each of these four samples were placed in a bath containing 400 grams of n-heptane and '70 grams of crotonaldehyde at 70 C. The four samples were re-, acted 2 minutes, 4 minutes, '7 minutes and 10 minutes and showed residual alcohol groups of 83%, 83%, 77% and 64%, respectively, calculated as vinyl alcohol.

I claim:

1. The process of water-insolubilizing a water soluble solid polyvinyl alcohol which comprises treating said solid alcohol with a solution of sulfuric acid and methanol, drying, and then heating it at a refluxing temperature in the presence of an acetallzation catalyst and an aldehyde in a hydrocarbon which is liquid at normal temperature and pressure until the reaction product is insoluble in water, thereby producing a polyvinyl acetal which is not soluble in said hydrocarbon, the base material and the final product being in the solid state throughout the process.

2. The process of water-insolubilizing a water soluble solid polyvinyl alcohol which comprises treating said solid alcohol with a solution of sulfuric acid and methanol,- drying, and then heating it at a refluxing temperature in the presence of anacetalization catalyst and an aldehyde in a paraffin which is liquid at normal temperature and pressure until the reaction product is insoluble in water, thereby producing a polyvinyl acetal which is. not soluble in said paraffin, the

- base material and the final product being in the solid state throughout the process.

3. The process of water-insolubilizing a water soluble solid polyvinyl alcohol which comprises treating said solid alcohol with a solutionof sulfuric acid and methanol, drying, and then heatin I it at a refluxing temperature in the presence of an aoetalizationcatalyst and an aldehyde in an aromatic liquid hydrocarbon until the reaction product is insolublein water, thereby producin a' polyvinyl acetal whichis not soluble in said hydrocarbon, the base material and the final product being in the solid state throughout the process.

4. The process of water-insolubilizing a water soluble solid polyvinyl alcohol which comprises treating said solid alcohol with a solution of sulfuric acid and methanol, drying, and then heating it at a refluxing temperature in the presence of an acetalization catalyst and an aldehyde in n-heptane until the reaction product isinsoluble in-water, therebyproducing a polyvinyl acetal which is not soluble in said n-heptane, the base material and the finalproduct being in the solid state throughout the process.

5. The Process of water-insolubilizing a water soluble solid polyvinyl alcohol which compnses treating said solid alcohol with a solution of sulfuric acid and methanol, drying, and then heating it at a refluxing temperature in the presence of an acetalization catalyst and an aldehyde in v toluol until the reaction product is insoluble in water, thereby producing a polyvinyl acetal which is not soluble in said toluol, the base material and the final product being in the solid state throughout the process.

6. The process of water insolubilizing a water soluble solid polyvinyl alcohol which comprises treating said solid alcohol with a solution of sulfuric acid and methanol, drying, and then heat,-

ing it at a refluxing temperature in the presence of an acetalization catalyst in a bath oi toluol and acetic acid containing paraformaldehyde until the reaction product is insoluble in water, thereby producing a polyvinyl acetal which is not soluble in said bath, the base material and the final product being in the solid state throughout the process.

JOSEPH DAHLE. 

